Preparation of n-butyraldehyde and/or n-butanol

ABSTRACT

A process for the preparation of n-butyraldehyde and/or n-butanol, in which 
     a) 1,3-butadiene is caused to react with an amine of the formula I 
     
         R.sup.1 R.sup.2 NH,                                        I 
    
      in which R 1  and R 2  independently denote hydrogen, optionally substituted aliphatic or cycloaliphatic radicals, or aryl or aralkyl radicals or are linked to form a bridging member which can contain hetero atoms, at elevated temperature and under superatmospheric pressure in the presence of a compound of a Group VIIIb element and in the presence of an alkali metal amide or a basic metal oxide to form a mixture of the adducts of the formulas II ##STR1##  and III ##STR2## b) the adduct III is isomerized to the adduct II, c) the adduct II is isomerized in the presence of a homogeneous or heterogeneous transition metal element catalyst in the liquid phase or in the presence of a heterogeneous catalyst containing a transition metal element in the gaseous phase to form the enamine of the formula IV ##STR3##  and d) n-butyraldehyde and/or n-butanol is/are produced from this enamine.

This is the U.S. National stage application of PCT/EP95/03358 filed Aug.24, 1995 now WO96/07630 published Mar. 14, 1996.

This is the U.S. National stage application of PCT/EP95/03358 filed Aug.24, 1995 now WO96/07630 published Mar. 14, 1996.

The present invention relates to a novel process for the preparation ofn-butyraldehyde and/or n-butanol and to the use of the n-butyraidehydesynthesized by the process of the invention for the preparation of2-ethylhexanol. The invention also relates to a process for thepreparation of 2-ethylhexanol from n-butyraldehyde.

n-Butyraldehyde and n-butanol are products which are produced on a largescale in the chemical industry and have varied uses. n-Butyraldehyde isproduced world-wide in amounts of more than 4 million t/yr and servesinter alia as starting material for the preparation of plasticizeralcohols. n-Butanol is employed on a large scale as solvent, for examplefor coating compositions.

n-Butyraldehyde is prepared nowadays on an industrial scale virtuallyexclusively by the hydroformylation of propene, for which purposevarious processes are used, which essentially make use of cobalt orrhodium hydroformylation catalysts, (Kirk-Othmer: Encyclopedia ofChemical Technology, 4th Edition, Vol. 4, pp. 741-746, John Wiley &Sons, New York 1992).

n-Butanol is one of the quantitatively most important derivatives ofn-butyraldehyde and is obtained therefrom by hydrogenation. Otherprocesses for the preparation of n-butanol, such as the hydrogenation ofcrotonaldehyde, which is in turn produced by aldol condensation ofacetaldehyde, are nowadays merely of historical interest or have onlyregional significance, such as in the case of the microbiologicalproduction of n-butanol by fermention of molasses, (Kirk-Othmer:Encyclopedia of Chemical Technology, 4th Edition, Vol. 4, pp. 694-696:John Wiley Sons, New York 1992). These processes, particularly thehydroformylation of propene, demand high investments, for example, forthe construction of high-pressure plant for the cobalt-catalyzedhydroformylation or for the purchase of the expensive rhodium catalyst,the plant required for handling during hydroformylation and for workingup the spent rhodium-containing catalyst solution. Furthermore thepreparation of n-butyraldehyde by the hydroformylation process requiresthe presence of a synthesis gas plant for the preparation of thesynthesis gas required for the hydroformylation. A further drawback ofthe process is the unavoidable formation of large quantities of theby-product isobutyraldehyde, which, on account of its restrictedpossibility of further usage in quantity, has a low economical rating.

1,3-Butadiene is a basic chemical which is produced in large amounts insteam crackers and is isolated, by extraction, from the C₄ cut obtainedin the cracker, for example, by means of N-methyl pyrrolidone. Although1,3-butadiene is available in large amounts and is a very cheap rawmaterial, no industrially usable process has been developed hitherto forthe preparation of n-butyraldehyde or n-butanol on the basis of1,3-butadiene. One reason for this is the tendency of 1,3-butadiene toundergo dimerization and polymerization reactions and the formation ofmixtures of 1,2- and 1,4-adducts in addition reactions. The reason forthis chemical behavior is the presence of two conjugated double bonds inthe 1,3-butadiene molecule (Kirk-Othmer: Encyclopedia of ChemicalTechnology, 4th Edition, Vol. 4, pp. 676-683, John Wiley & Sons, NewYork 1992).

U.S. Pat. No. 3,391,192 discloses that amines react with 1,3-butadienein the presence of alkali metal amides to form the corresponding allylamines. Falk at al (J. Org. Chem. 37, 4243 (1972)) investigated thelithium amide-catalyzed additon of amines to butadiene in relation tothe solvent and the amine. Kanuno and Hattori (J. Catal. 85 (1984) 509)describe the catalyzed reaction of butadiene with amines using solidbase catalysts such as MgO or CaO. In their experiments, the reactionmixture is passed through a circulated gas reactor over a fixed bedunder a total pressure of 100 torr. According to U.S. Pat. No.4,675,307, strongly basic hydrotalcites are suitable for use ascatalysts for the hydroamination.

Transition metal complexes have also been used as catalysts for theaddition of amines to 1,3-butadiene. Watanabe et al (Kenkyu Kokoku-AsaliGarasu Kogyo Gijiutsu Shoreikai 38, 111 (1981)) describe the reaction ofvarious primary and secondary amines with butadiene in the presence ofpalladium and platinum complexes. Secondary amines mainly yield butenylamines, depending on the type of catalyst used, whereas primary aminesproduce mixtures of 1:1 adducts with 1:2 adducts and 1:4 adducts. JP-A71/19,925, JP-A 71/19,926, and JP-A 72/25,321 relate to the catalyzedsynthesis of alkenyl amines using palladium compounds and chelatingphosphine ligands. Takahashi et al (Bull. Chem. Soc. Jap. 45, 1183(1972)) carry out this reaction in the presence of, in addition, sodiumphenolate/phenol. Another known co-catalyst for palladium-catalyzedhydroamination is triethylammonium iodide (Arbruster et al, Organomet.5, 234 (1986)), which is used to increase the selectivity of thereaction toward the monoadduct. U.S. Pat. No. 4,120,901 discloses thatthe addition of ammonia to produce 1-aminobutene-2 is successfullycarried out using palladium complexes in primary or secondary alcoholsacting as solvent. The amination of 1,3-dienes in the presence ofoptically active phosphorus compounds is described in U.S. Pat. No.4,204,997.

Ligand effects of the rhodium-catalyzed reaction of butadiene withamines has been investigated by Baker and Halliday (Tetrahedron Lett.2773 (1972)). EP-A 176,398 reveals the successful reaction of secondaryamines with 1,3-butadiene in the presence of water-soluble rhodiumcomplexes. Co-catalysts used in this case are trisulfonated phosphines.Herrmann et al (Angew. Chem. 102, 408 (1990)) make use of appropriatewater-soluble platinum complexes for the reaction of isoprene withdimethylamine.

In addition to the said transition metals, it is known to use compoundsof nickel, cobalt, or iridium for such hydroaminations. Thus Baker et al(J. Chem. Soc. Perkin II, 1511 (1 974)) have investigated the reactionof butadiene in the presence of catalytic amounts of nickelacetylacetonate and phosphite ligands. The same reaction, carried outusing cobalt or iridium catalysts, produces mixtures of 1:2 adducts with1:1 adductsFor the isomerization of allyl ethers to anamines a series ofreagents has already been examined.

The isomerization of 1-N-pyrrolidino-2-prepene using basic heterogeneousoxide catalysts such as MgO, CaO, or BaO is described by Hattori et al(J. Catal. 65, 245 (1980)). Hubert (J. Chem. Soc. (C), 2048 (1968))effects the rearrangement of allyamines in the presence of patassiumamide supported on aluminum oxide.

Apart from the said heterogeneous catalysts, use has been made ofhomogeneous catalysts for the isomerization of allylamines in the liquidphase.

Strong bases soluble in the organic medium, such as potassiumtert-butanolate, have been investigated by Price et al (TetrahedronLett. 2863 (1 966)) and Martinez (Tetrahedron 34, 3027 (1978)) for theconversion of allylamines to enamines.

Not only such base-catalyzed reactions but also reactions involving theuse of transition metal compounds are described.

Isomerizations of secondary and tertiary allylamines usingrhodium/diphosphine complexes to produce enamines or imines aredescribed by Otsuka et al (J. Am. Chem. Soc. 106, 5208 (1984)) and bySchmid et al (Helv. Chim. Acta. 73, 1258 (1990)); Helv. Chim. Acta 74,370 (1991)). U.S. Pat. No. 4,861,890, EP-A 0,068,506, EP-A 257,411, andOtsuka (Org. Synth. 67, 33 (1989)) disclose that β,γ-unsaturated aminesisomerize to enamines in the presence of rhodium/diphosphine complexes,which enamines are converted to their corresponding aldehydes onhydrolysis. JP-A 79/5907 and Otsuka (J. Am. Chem. Soc. 100, 3949 (1978))teach the cobalt/phosphine complex-catalyzed rearrangement ofallylamines.

In addition to said compounds, use can be made of molybdenum compounds(Tatsumi et al, J. Organomet. Chem. 252, 105 (1983)) or rutheniumcompounds (EP-A 398,132; Doering et al, J. Am. Chem. Soc. 107, 428(1985)).

The direct single-stage conversion of allylamines to the correspondingaldehydes or alcohols is not known.

It was thus the object of the present invention to provide an economicalprocess which can be employed on an industrial scale for the preparationof n-butyraldehyde and/or n-butanol, which makes it possible to preparethese products at high yield and selectivity. In particular, the amountof by-product formed in the process should be low or the saidby-products should themselves be sought-after commercial products.Furthermore the process should be flexible so as to make it possible toprepare n-butyraldehyde and/or n-butanol as required, in accordance withthe demand for these compounds. The process should not demand thepresence of a synthesis gas plant or necessitate the use of highpressure facilities.

2-Ethylhexanol is manufactured on an industrial scale via the aldolreaction of n-butyraldehyde followed by hydrogenation of the aldolproduct (Kirk-Othmer, Encyclopedia of Chemical Technology 4th Edition,1991, Vol. 1, p 893; Ullmanns Encyklopadie der techn. Chemie, 4thEdition, 1974, Vol. 4, p 214). The alcohol is used in the synthesis ofthe plasticizer bis(2-ethylhexyl)phthalate.

Thus another object of the invention is to provide a process by means ofwhich n-butyraldehyde can be converted to 2-ethylhexanol withoutintermediate, energy-consuming purification.

Accordingly, we have found a process for the preparation ofn-butyraldehyde and/or n-butanol, wherein

a) 1,3-butadiene is caused to react with an amine of the formula I

    R.sup.1 R.sup.2 NH,                                        I

in which R¹ and R² independently denote hydrogen, optionally substitutedaliphatic or cycloaliphatic radicals, or aryl or aralkyl radicals or arelinked to form a bridging member which can contain hetero atoms, atelevated temperature and under superatmospheric pressure in the presenceof a compound of a Group VIIIb element and in the presence of an alkalimetal amide or a basic metal oxide to form a mixture of the adducts ofthe formulas II ##STR4## and III ##STR5## b) the adduct III isisomerized to the adduct II, c) the adduct II is isomerized in thepresence of a homogeneous or heterogeneous transition metal elementcatalyst in the liquid phase or in the presence of a heterogeneouscatalyst containing a transition metal element in the gaseous phase toform the enamine of the formula IV ##STR6## and d) n-butyraldehydeand/or n-butanol is/are produced from this enamine IV by the reactionthereof with hydrogen and water or water only in the presence of ahomogeneous or heterogeneous transition metal element catalyst in theliquid phase or in the presence of a heterogeneous transition metalelement catalyst in the gaseous phase and in the presence of an acid orin the presence of one of said catalysts and an acid, and the amine I isagain liberated, and the liberated amine I is recycled to the stagedefined above as partial reaction a).

We have also found a method of using the n-butyraldehyde synthesized bythe process of the invention for the preparation of 2-ethylhexanol, anda process for the preparation of 2-ethylhexanol.

The process of the invention for the preparation of n-butyraldehydeand/or n-butanol is thus composed of four partial reactions a) to d).The reactions c) and d) can be carried out individually, successively,in at least 2 process stages or virtually simultaneously in a singleprocess stage, as required. The same applies to the reactions a) and b),in which case the isomerization of the adduct III to the adduct II inaccordance with partial reaction b) takes place following recycling ofthe adduct III to the process stage involving the addition of the amineR¹ R² NH to 1,3-butadiene concurrently with the addition reactiondefined as partial reaction a). By this means it is a simple matter toadjust the process perameters for the process of the invention to thelocal conditions at the site where a plant for carrying out the processis installed, for example by integrating plant units already present atthe site in the system required for the process of the invention.

The term "process stage" is used in this application for a plant unit,in which any one of the reactions a) to d) takes place over thecatalyst(s) employed in this plant unit or in which a number,particularly two, of these reactions, occur in parallel over thecatalyst(s) used in this plant unit. The hydrolysis or the combinedhydrolysis/hydrogenation of the enamine IV defined as partial reactiond) is, unless otherwise stated in this application, considered to be anindividual reaction.

If the catalyst used in a plant unit or if each of the catalysts used ina plant unit is capable of catalyzing, under the reaction conditionsused therein, for example, the isomerization of the adduct II to theenamine IV defined as partial reaction c) and the hydrolysis orhydrogenation of the enamine IV to n-butyraldehyde and/or n-butanoldefined as partial reaction d), so that no strict spatial separation ofthese reactions in the unit can be ascertained, this application speaksof the execution of the reactions c) and d) as being in a `singleprocess stage`. A unit can include both a single reactor and a number ofin-line reactors, which are filled with the same or, optionally,different catalysts and are operated in the same mode of operation andunder the same or different temperature and pressure conditions. By`mode of operation` we mean operating either in the liquid phase using ahomogeneous catalyst or operating in the liquid phase using aheterogeneous catalyst or operating in the gaseous phase. It followsthen that this application will not speak of, for example, a `reactionin a single process stage`, if in the individual successive reactorscatalysts are used, which are capable only of catalyzing one specificreaction or if these reactors are operated with different operationalmodi.

The process of the invention is described in greater detail below:

In the process stage a) 1,3-butadiene is caused to react with the amineR¹ R² NH I in the presence of a catalyst according to equation (1)##STR7## to form the mono-adducts of formulas II and III and, when useis made of a primary amine or ammonia, to further form mixtures ofdi-adducts and tri-adducts and also to form telomers. In the resultingmono-adduct II the double bond can be present in both the cis and transforms, but this bears no relevance on the further course of the process.The adducts II and III are formed, depending on the reaction conditionsand catalyst used, generally in a molar ratio of from 1:1 to 20:1.

The nature of the amine R¹ R² NH I employed in the reaction is notusually crucial for the process. Ammonia and both primary and secondaryamines can be used. The amines can carry a number of different radicalsR¹ and R². Suitable radicals are, therefore, aliphatic radicals such asalkyl radicals, in particular C₁ -C₂₀ alkyl radicals, and C₂ -C₂₀alkenyl radicals, and also cycloalkyl radicals, in particular C₄ -C₁₀cycloalkyl radicals, and C₄ -C₁₀ cycloalkenyl radicals. The non-cyclicradicals may be linear or branched. The aliphatic radicals can carrysubstituents which are inert under the conditions of the reaction,preferably one or two such substituents, examples of which are C₁ -C₁₀alkoxy groups, amino groups, and hydroxy groups. The radicals R¹ and R²may also independently stand for aryl groups, preferably C₆ -C₁₀ arylsuch as phenyl, which aryl groups may be substituted by inert radicalssuch as C₁ -C₄ alkyl. Aralkyl radicals, preferably C₇ -C₁₁ aralkyl, arealso suitable as substituents on the amine I.

The radicals R¹ and R² may also be linked to form a bridging member soas to form a nitrogen-containing ring. The number of bridging atoms ispreferably from 3 to 6. The bridging member can contain hetero atomssuch as oxygen or nitrogen. It may be saturated or unsaturated or bepart of an aromatic ring. In addition, it can carry inert substituentssuch as C₁ -C₄ alkyl groups.

Ammonia, C₁ -C₆ N-alkylanilines, and amines are particularly preferred,in which the radicals R¹ and R² independently stand for branched-chainor straight-chain C₁ -C₆ alkyl radicals, C₂ -C₆ alkenyl radicals, or C₄-C₇ cycloalkyl radicals.

The following is a list of amines which can be used in the presentinvention, given by way of example only:

Methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine,isobutylamine, sec-butylamine, tert-butylamine, isopentylamine,3-methyl-2-butylamine, n-hexylamine, octylamine, 2-ethylhexylamine,decylamine, tert-hexylamine, 1,1,3,3-tetramethylbutylamine, allylamine,2-butenylamine, 3-pentenylamine, hexylamine, n-heptylamine,cyclopentylamine, cyclohexylamine, methylcyclohexylamine,cyclooctylamine, cyclodecylamine, benzylamine, 2- phenylethylamine,4-methoxyphenylethylamine, aniline, toluidine, 2-diethylaminoethylamine,dimethylaminopropylamine, 2-aminoethanol, 1-amino-2-propanol,3-aminopropanol-1, 2-aminobutanol-1, dimethylamine, diethylamine,di-n-propylamine, diisopropylamine, di-n-butylamine, diisobutylamine,di-sec-butylamine, di-n-pentylamine, diisopentylamine, di-n-hexyl-amine,di-2-ethylhexylamine, n-methylbutylamine, n-ethylbutylamine,di-2-methoxyethylamine, n-methylcyclohexylamine, n-ethylcyclohexylamine,n-methylethylamine, dicyclohexylamine, n-ethylaniline, diamylamine,di-n-octylamine, allylmethylamine, 2-butenylethylamine, dialkylamine,n-methylbenzylamine, allylmethallylamine, pyrrolidine, piperidine,4-methylpiperidine, morpholine, 2,6-dimethylmorpholine, imidazol,2-methylimidazol, 4-methylimidazol, piperazine, 1 -ethylpiperazine,pyrazol, ethylenediamine, 1,3-diaminopropane, 1,2-propyidiamine,neopentandiamine, hexamethylenediamine, diethylenetriamine

A large number of transition metal element catalysts can be used inprocess stage a), for example, compounds of palladium, platinum, nickel,rhodium, cobalt, or iridium, or strongly basic compounds such as metalamides, metal alcoholates, and hydrotalcites.

In one embodiment of the process of the invention the addition of theamine I can be effected by means of a catalyst homogeneously dissolvedin the reaction medium or a heterogenized transition metal elementcatalyst, which catalyst contains a Group VIIIb element such aspalladium, platinum, nickel, rhodium, rhenium, cobalt, or iridium,preferably palladium or nickel.

Advantageously, these transition metal element catalysts, particularlythe palladium and nickel catalysts, are used in the form of theircomplexes with, e.g., phosphine ligands, 2,2'-bipyridine ligands, or1,10-phenanthroline lagands, such complexes being homogeneously solublein the reaction medium. In the process of the invention a large numberof different phosphine ligands, 2,2'-bipyridine ligands, or1,10-phenanthroline lagands can be used for the purpose of complexingthe Group VIIIb metals, particularly palladium and nickel. Suitableligands are both monodentate and polydentate, particularly bidentate,phosphine ligands. Suitable ligands are, e.g., trialkyl phosphines,triaryl phosphines, alkyldiaryl phosphines, aryidialkyl phosphines, aryldiphosphines, alkyl diphosphines, and arylalkyl diphosphines. The alkylgroup-carrying ligands may contain the same or different C₁ -C₁₀,preferably C₁ -C₆, alkyl or cycloalkyl groups. The aryl group-carryingligands can contain the same or different C₆ -C₁₂ aryl groups,particularly the phenyl or naphthyl group, or alternatively diphenylgroups. Furthermore ligands for complexing the Group VIIIb elements canbe used which carry heterocyclo-aliphatic groups such as pyrrolidine,imidazolidine, piperidine, morpholine, oxazolidine, piperazine, ortriazolidine groups or heteroaromatic groups such as pyrrole, imidazole,oxazole, indole, pyridine, quinoline, pyrimidine, pyrazole, pyrazine,pyridazine, or quinoxaline groups together with other alkyl or arylgroups. The alkyl or aryl groups of the ligands can be unsubstituted orcarry substituents which are inert under the reaction conditions, suchas C₁ -C₆ alkyl, nitro, cyano or sulfonate groups.

Theoretically there is no limit to the usability of such ligands forcomplexing the Group VIIIb elements, particularly palladium and nickel,in the process of the invention. However for reasons of cost it ispreferred to use ligands which can be prepared in a simple manner. Alist of such ligands is given below merely by way of example:

trimethylphosphine, triethylphosphine, tripropylphosphine,triisopropylphosphine, tributylphosphine, trioctylphosphine,tridecylphosphine, tricyclopentylphosphine, tricyclohexylphosphine,triphenylphosphine, tritolylphosphine, cyclohexyldiphenylphosphine,tetraphenyldiphosphinomethane, 1,2-bis(diphenyl-phosphino)ethane,tetramethyidiphosphinomethane, tetraethyldiphosphinomethane,1,3-bis(diphenylphosphino)propane, 1,4-bis(diphenylphosphino)butane,bis(di-tert-butyldiphosphino)methane, 1,2-bis( dimethylphosphino)ethane,1,2-bis(diethylphosphine)ethane, 1,2-bis(dipropylphosphino)ethane,1,2-bis(diisopropylphosphino)ethane, 1,2-bis(dibutylphosphino)ethane,1,2-bis(di-tert-butylphosphino)ethane,1,2-bis(dicyclohexylphosphino)ethane, the salts of triphenylphosphinetrisulfonate or of triphenylphosphine monosulfonate, as well as thebisphosphine ligands described in EP-A 279,018, EP-A 311,619, WO90/06810 and EP-A 71,281. Apart from using the processes described inthe aforementioned patent applications, the alkyl or aryl phosphineligands can be prepared by conventional methods as described, forexample, in Houben-Weyl, Methoden der Organischen Chemie, Vol. XII/1,4th Edition, pp. 17-65 and pp. 182-186, Thieme, Stuttgart, 1963 and Vol.E 1, 4th Edition, pp. 106-199, Thieme, Stuttgart, 1982.

In addition to phosphine ligands use can be made in the process of theinvention, to advantage, of 2,2'-bipyridine or 1,10-phenanthrolineligands of alkyl- or aryl-substituted or anellated 2,2'-bipyridine or1,10-phenanthroline derivatives, which contain the (--N═C--C═N--)grouping responsible for the complexing property of the 2,2'-bipyridineor 1,10-phenanthroline ligands, for example, 2,2'-biquinoline,4,7-diphenyl-1,10-phenanthroline, 4,5-diazafluorene, dipyrido3,2a:2',3'-c!phenazine, 2,2',6',2"-terpyridine and the like. Some ofthese ligands are commercially available, e.g., 2,2'-bipyridine or1,10-phenanthroline, or can be prepared by the methods described inSynthesis 1, (1976) or Aust. J. Chem. 23, 1023 (1970).

The complexes of Group VIIIb elements, particularly of palladium andnickel, which can be used in the process of the invention for thepartial reaction a) can be produced in situ in the reaction mixture orbe preformed and added to the reaction mixture. For the formation insitu of these complexes it is general to operate in such a manner thatcompounds of the Group VIIIb elements, e.g., their halides, preferablytheir chlorides, bromides, or iodides, the nitrates, cyanides orsulfates, or complex compounds of these metals, such asacetylacetonates, carboxylates, carbonyl complexes or olefin complexes,such as ethers or butadiene complexes, are fed in to the reactionmixture together with the respective ligands, after which the complexesthat can be used in the invention in partial reaction a) are formed inthe reaction mixture. In this method the complexing agent is generallyadded in a molar ratio with respect to the Group VIIIb element of from2:1 to 200:1, preferably from 2:1 to 10:1, and more preferably from 2:1to 4:1.

Generally, when effecting the addition of the amine R¹ R² NH to1,3-butadiene in process stage a) of the process of the invention, whenuse is made of the said Group VIIIb element komplex catalysts,particularly the palladium complex catalysts, a molar ratio of1,3-butadiene to Group VIIIb element of from 100:1 to 100,000:1,preferably of from 200:1 to 10,000:1 and more preferably of from 400:1to 5000:1 is used, and when the process is carried out continuously thismolar ratio is based on the steady 1,3-butadiene concentration in theliquid reaction mixture.

The molar ratio of amine R¹ R² NH to 1,3-butadiene can, in thisembodiment of the process, be chosen within wide limits and is usuallynot critical. For example, the amine to be added to 1,3-butadiene canfunction not only as a reagent but also as a solvent for the complexcatalyst. Generally therefore the process of the invention uses in thepartial reaction a) a molar ratio of amine to 1,3-butadiene of from0.5:1 to 10:1, preferably from 1:1 to 5:1 and more preferably from 1:1to 5:1, whilst in the case of the continuous embodiment of the processthese figures relate to the steady 1,3-concentration in the liquidreaction mixture.

The addition of the amine R¹ R² NH to 1,3-butadiene defined as partialreaction a) of the process of the invention with the aid of the complexcatalysts mentioned above is preferably carried out in the liquid phase.Generally the catalyst is dissolved in the liquid reaction medium usedas initial substance and 1,3-butadiene is introduced into the reactionmixture in liquid or gaseous form, together with the alcohol. Thereaction medium used can be the amine to be added to 1,3-butadiene or asolvent that is inert under the reaction conditions, preferably ahigh-boiling solvent. Examples of suitable solvents are condensationproducts which are formed during the reaction, such as amino octadienes,alkoxy dodecatrienes, and also ethers, such as dibutyl ether, diethyleneglycol dibutyl ether, low molecular weight poly(ethylene glycol ether)sas well as alcohols, such as methanol or butanol.

When the process is carried out batchwise, the reaction is generallycarried out in a stirred autoclave. The adducts of formulas II and IIIformed during this process are then advantageously separated from thereaction mixture by distillation, whilst the homogeneous catalystcontaining the Group VIIIb element, particularly palladium or nickel,remains at the bottom of the distillation column, dissolved in thehigh-boiling solvent. The catalyst solution thus remaining at the baseof the distilling apparatus can be re-used for further reactions.

When the process is carried out continuously, the 1,3-butadiene isintroduced, preferably in liquid form under pressure, into the reactionmixture containing the amine R¹ R² NH and the homogeneously dissolvedtransition metal element catalyst as well as any high-boiling solvent.The reaction is advantageously carried out in a tubular reactor or loopreactor or, preferably, in a cascade of reactors. Unconverted1,3-butadiene is advantageously recycled during this process. The amineis advantageously continuously metered into the reaction mixture at therate at which it is consumed in the reaction, such that it is alwayspresent in stoichiometric excess.

In another continuous embodiment of the process of the invention the1,3-butadiene can be passed in the gaseous state through the liquidreaction medium containing the catalyst, whilst unconverted1,3-butadiene is used to strip the relatively readily volatile adductsof the formulas II and III which are formed with the amine during thereaction, from the reaction mixture. The amine I can be continuouslyadded to the reaction mixture during this process, at a ratecorresponding to its rate of consumption during the reaction.

The addition of the amine R¹ R² NH to 1,3-butadiene in the presence ofthe said complexes of the Group VIIIb elements, particularly palladiumor nickel, is generally carried out at a temperatur of from 20° to 180°C., preferably from 50° to 150° C. and more preferably from 80° to 120°C. and under a pressure preferably of from 6 to 50 bar and morepreferably under autogenous pressure.

In the process of the invention it is advantageous for the addition ofthe amine R¹ R² NH to 1,3-butadiene in partial reaction a) to useheterogenized complex catalysts, preferably those in which the GroupVIIIb element, particularly palladium or nickel, is attached topolymeric matrices. Such polymeric matrices can be resins, such asstyrene-divinylbenzene resins or phenol-formaldehyde resins, to whichthe respective chelate ligands, i.e. phosphines, 1,10-phenanthrolines or2,2'-bipyridines, are attached, which on the other hand form complexeswith the Group VIIIb elements, particularly palladium or nickel, andthus quasi immobilize them. Suitable heterogeneous matrices for theimmobilization of the Group VIIIb element complexes, particularly thepalladium and nickel complexes, are inorganic support materials,following previous hydrophobization and chemical modification of theirsurface by means of organic reagents. Such heterogenized, polymericallyattached Group VIIIb element complexes, particularly palladium andnickel complexes, can be obtained, for example, by the process describedin Zhuangyu et al (Reactive Polymers 9, 249 (1988)). Immobilizedcomplexes of the Group VIIIb elements can be obtained e.g., by theprocesses described in Hartley, Adv. Organomet. Chem. 15, 189 (1977), F.R. Hartley "Supported Metal Complexes", Riedel, Dordrecht 1985, K.Smith, "Solid Supports and Catalysis in Organic Synthesis", EllisHorwood, Prentice Hall, N.Y. 1992; C. H. Pittman "Polymer supportedReactions in Organic Synthesis", p. 249, Wiley, Chichester 1980 and C.H. Pittmann, Am. Chem. Soc. 98, 5407 (1976) as well as Am. N.Y. Acad.Sci. 245, 15 (1977). The advantage of the use of such heterogenizedcatalysts lies particularly in the greater ease of separation of thecatalyst from the reaction products and the more gentle separationachieved. This catalyst can be in the form of a fixed bed through whichthe reaction mixture flows or it can alternatively be suspended in thereaction mixture and mechanically separated therefrom on completion ofthe reaction.

In another embodiment of the process stage a) the reaction between1,3-butadiene and the amine R¹ R² NH I can be carried out in thepresence of an alkali metal amide. Those amides which correspond to theamines R¹ R² NH are preferred. These can be synthesized in situ or exsitu, the preparation in situ being preferred for practical reasons.They are prepared from the amine R¹ R² NH and a strong base generallyhaving a pk_(a) value above 20. Suitable strong bases areorgano-alkali-metallic compounds such as phenyl sodium, n-butyl lithium,sec-butyl lithium, methyl lithium, naphthalides of lithium, sodium, orpotassium, graphite compounds such as C₈ K and C₂₄ K, and also thehydrides of lithium, sodium, and potassium. Alternatively, the alkalimetals themselves can be caused to react with the amines to form thecorresponding amides. The alkali metal amides may be used in catalyticand stoichiometric amounts, catalytic amounts being preferably from0.001 to 0.1 mol per mole of amine. It has been found to be advantageousto pass butadiene into a quantity of a mixture of amine R¹ R² NH and thecorresponding amide and to remove the adducts II and III formed, bydistillation. Conventional reactors such as bubble-cap columns or loopreactors may be used. Alternatively, a cascade of stirred boilers can beemployed. The reaction can be carried out continuously or batchwise. Thepressure and temperature ranges involved in this embodiment are the sameas those stated above for the reaction of butadiene and amine R¹ R² NHin the presence of a compound of a Group VIIIb element.

Furthermore, the synthesis of the adducts II and III can be effectedunder the above conditions in the presence of basic metal oxides such asMgO, CaO, SrO, La₂ O₃, and hydrotalcite. The metal oxides can be used insubstance or supported on inert supports.

Instead of using pure 1,3-butadiene there can be used in the process ofthe invention 1,3-butadiene-containing hydrocarbon streams as rawmaterial. Such streams are produced, for example, as a so-called C₄ cutin steam crackers. Advantageously these streams are, prior to use in theprocess of the invention, relieved of any acetylenic or allenichydrocarbons contained therein, by partial hydrogenation (Weissermel,Arpe: Industrielle Organische Chemie; 3rd Edition, VCHVerlagsgesellschaft, Weinheim 1988). The 1,3-butadiene-containingstreams can then be introduced in a similar manner to the pure1,3-butadiene into the partial reaction a) of the process of theinvention. Advantageously the saturated or monoolefinic hydrocarbonscontained in these hydrocarbon streams which have not reacted during thereaction taking place in partial reaction a) are removed from theeffluent from partial reaction a), for example by means of a gas/liquidseparator. The adducts of formulas II and III obtained in the reactionof these streams in partial reaction a) of the process of the inventioncan be further processed, as described below, to form n-butyraldehydeand/or n-butanol, in the same manner as the adducts II and III producedwith pure 1,3-butadiene in reaction a).

The effluent from partial reaction a) of the process of the inventiongenerally contains, in addition to unconverted 1,3-butadiene, theadducts of formulas II and III as well as, possibly, particularly whenusing transition metal catalysts in partial reaction a), isomers of therespective aminooctadiene, which are referred to below collectively as"aminooctadiene". The aminooctadiene forms by telomerization in a sidereaction. In addition to these constituents, the effluent from partialreaction a) can contain small amounts of other by-products, for example,octatriene and vinylcyclohexene. The formation of these by-products canbe influenced and if desired minimized by controlling the type ofreaction to take place in partial reaction a), for example, bymanipulating the 1,3-butadiene-to-amine R¹ R² NH ratio in the reactionmixture, the temperature of reaction, and the pressure.

The adduct required for the preparation of n-butyraldehyde and/orn-butanol in the process of the invention is the 1-aminobutene-2 offormula II, which, for the preparation of the target compounds, can beseparated in the process of the invention from its isomer3-aminobutene-1 of formula III also present in the effluent. Since theadducts II and III are formed in various molar ratios depending on thereaction conditions, the process according to the invention would beuneconomical on an industrial scale, if it were not posible to convertthe 3-aminobutene-1 III in an economical manner to the desired1-aminobutene-2 II.

For this purpose, the adduct III is initially separated from theisomeric adduct II present in the effluent coming from the partialreaction a). This can advantageously be effected by passing the effluentfrom partial reaction a), after previously removing unconverted1,3-butadiene, e.g., in a gas-liquid separator or a pressure column, toa distillation apparatus and effecting the desired separation therein byfractional distillation.

This fractional distillation can also be utilized to separate the adductII from the by-products present in the effluent from partial reactiona), i.e., 1,3-butadiene dimers and trimers. Since these by-productsgenerally have no adverse effect on the rest of the process of theinvention, separation thereof can be omitted. Alternatively, thedistillation may be operated such that in addition to the adduct IIIonly some of the by-products, particularly the olefinic 1,3-butadienedimers are separated, whilst other by-products, particularly theaminooctadiene, are processed together with the adduct II in thesubsequent partial reactions, the end products formed from theseby-products from the partial reaction a) being octanols, which aredesirable plasticizer alcohols.

The separation, by distillation, of the readily volatile adduct III fromthe adduct II can be carried out in a simple manner, e.g., inconventional distillation columns. The adduct III separated from thedesired adduct can, as also the unconverted 1,3-butadiene, then berecycled to the partial reaction process stage a) of the process of theinvention. Recycling of the adduct III to the process stage defined asthe partial reaction a) of the process of the invention causesisomerization of the adduct III to adduct II in this process stage andeventually leads to the suppression of re-formation of the undesirableadduct III, so that when use is made of this recycling method, theoverall balance of this cyclic process virtually displays only thedesired adduct II and not its undesirable isomer III.

Alternatively, instead of recycling it to the partial reaction processstage a) of the process according to the invention, the adduct III canbe isomerized in a separate isomerization process stage by passing theadduct III separated from the adduct II through, e.g., a reactor filledwith one of the catalysts suitable for use in partial reaction a),separating the effluent from this reactor, which consists of theisomerization mixture of adduct III and adduct II formed therein, intoadduct II and adduct III, for example, by distillation, processing theresulting adduct II to n-butyraldehyde and/or n-butanol in the remainingprocess stages of the process of the invention and recycling the adductIII back to the isomerization reactor.

The isomerization of the adduct III to adduct II in the isomerizationreactor can take place in the presence or absence of a solvent. It ispreferred to carry out this reaction without the use of solvents. If theisomerization is carried out in the presence of a solvent, those usedare generally high-boiling solvents such as ethers, for example, di- ortri-ethylene glycol dimethyl ether, di- or tri-ethylene glycol dibutylether, high-boiling aromatic or aliphatic hydrocarbons or halogenatedaliphatic or aromatic solvents, e.g., dichlorobenzene. The use oflow-boiling solvents is possible but usually entails an increase inenergy expenditure during distillation of the effluent from the reactorto separate it into the adducts II and III.

In the continuation of the process of the invention for the preparationof n-butyraldehyde and/or n-butanol the adduct II is catalyticallyisomerized in the partial reaction c) to form the enamine of formula IV,which is then catalytically hydrolyzed in partial reaction d) in thepresence of water to form n-butyraldehyde and/or is catalyticallyconverted to n-butanol in the presence of water and hydrogen and/or ishydrolyzed to n-butyraldehyde in the presence of water. The reactions c)and d) in the process of the invention can be effected, as desired,successively in two process stages or successively in a single reactoror, particularly advantageously, as a one-shot process effected in asingle process stage. Both reactions c) and d) can take place in thegaseous phase or in the liquid phase.

As just mentioned, the reactions c)--the isomerization of the adduct IIto form the enamine IV--and d)--its reaction with water or hydrogen andwater to form n-butyraldehyde and/or n-butanol--are carried out in asingle process stage or in a number of process stages. As a result,these process stages encompass the following chemical reactions asdepicted in the reaction equation (2) ##STR8##

The last reaction step in each case, i.e. the hydrolysis of the enamineIV to n-butyraldehyde on the one hand or the combinedhydrolysis/hydrogenation of the enamine IV to n-butanol on the otherhand, can, by selecting appropriate reaction conditions, particularly byselecting a suitable catalyst or acid and controlling the amount of thereactants water and hydrogen made available during the reaction, arecontrolled in such a manner that either the end product n-butyraldehydeor the end product n-butanol is selectively formed or that mixtures ofthese two desired products are formed as end product of the process ofthe invention.

We have found, surprisingly, that the catalysts which catalyze theisomerization of the adduct II to the enamine IV, generally also workwell as catalysts for the hydrolysis of the enamine IV ton-butyraldehyde or for the combined hydrolysis/hydrogenation of theenamine IV to n-butanol. Accordingly, in a particularly preferredembodiment of the process of the invention, i.e. the execution of thereactions c) and d) in a single process stage, the same catalysts areused both for the preparation of the end product n-butyraldehyde and forthe preparation of the end product n-butanol.

Both the isomerization of the adduct II to the enamine IV and thehydrolysis of the enamine IV to n-butyraldehyde or the combinedhydrolysis/hydrogenation of the enamine IV to n-butanol can be carriedout in the gaseous phase or in the liquid phase. When carrying out thesereaction steps in a single process stage in the liquid phase bothhomogeneous and heterogeneous catalysts can be used. If these processstages are operated in the gaseous phase, heterogeneous catalysts aregenerally preferred.

The homogeneous catalysts used for the isomerization of the adduct II tothe enamine IV and its hydrolysis or combined hydrolysis/hydrogenationto n-butyraldehyde and/or n-butanol in a single process stage comprise alarge number of transition metal element compounds, particularly thosecontaining Group VIb, VIIb, and VIIIb elements, preferably chromium,molybdenum, tungsten, rhenium, iron, cobalt, nickel, ruthenium, rhodium,palladium, platinum, osmium, and/or iridium.

Suitable catalysts are, for example, the salts of these transitionmetals, particularly their halides, nitrates, sulfates, phosphates, orcarboxylates soluble in the reaction medium, for example, their C₁ -C₂₀carboxylates, such as formates, acetates, propionates,2-ethylhexanoates, and also the citrates, tartrates, malates, malonates,maleates, or fumarates, sulfonates, for example, methanesulfonates,benzenesulfonates, naphthalenesulfonates, toluenesulfonates, ortrifluoromethanesulfonates, cyanides, tetrafluoroborates, perchlorates,or hexafluorophosphates, also soluble salts of the oxy-acids of thesemetals, particularly the alkali metal, alkaline earth metal, or oniumsalts, such as ammonium, phosphonium, arsonium, or stibonium salts, ofvanadium oxy-acids, rhenium oxy-acids, or perrhenic acid, or theanhydrides of these acids, particularly dirhenium heptoxide, solubleinorganic complex compounds of these elements, particularly their aquo,ammine, halo, phosphine, phosphite, cyano, or amino complexes as well asthe complexes of these transition metals with chelating agents such asacetylacetone, dioximes, for example, diacetyldioxime, furildioxime, orbenzildioxime, ethylenediaminetetraacetic acid, nitrilotriacetic acid,nitrilotriethanol, ureas or thioureas, bisphosphines, bisphosphites,bipyridines, terpyridines, phenanthrolines, 8-hydroxyquinoline, crownethers or poly(alkylene glycol)s, as well as organometallic compounds ofthese transition metal elements, for example, carbonyl complexes such as

HRuCl₂ (CO)₂ (PPh₃)₂,

RuH₂ (CO)( PPh₃)₃,

HRuCl(CO)(hexyldiphenylphosphine)₃,

RuH₂ (CO)(PPh)₃,

HRh(CO)(PPh)₃, or

IrCl(CO)(PPh₃)₃,

the abbreviation PPh₃ designating triphenylphosphine, also

RuH₂ (PPh)₃,

HRhCl(PPh₃)₃,

Fe₂ (CO)₉ or

Fe₃ (CO)₁₂,

organotrioxorhenium(VII) compounds such as

C₁ -C₄ alkyltrioxorhenium(VII),

particularly methyltrioxorhenium(VII),

cyclopentadienyltrioxorhenium(VII), or

phenyltrioxorhenium(VII).

Preferred salt-like homogeneous catalysts are the halides, particularlythe chlorides, nitrates, sulfates, carboxylates, and cyanides ofrhodium, ruthenium, palladium, platinum, iridium, rhenium, and vanadiumas well as the alkali metal, alkaline earth metal, ammonium,alkylammonium, arylammonium, arylphosphonium, and alkylphosphonium saltsof vanadic acids, particularly their monovanadates and correspondingsalts of rhenic acids, particularly their rhenates(IV), rhenates(VI) andperrhenates.

Another suitable homogeneous catalyst is dirhenium heptoxide (Re₂ O₇).

Inorganic complex compounds preferably used in the process of theinvention for carrying out the reactions c) and d) are, e.g., rutheniumtrichloride, rhodium trichloride, and iridium hexaquoditosylate.

Organo-transition-metal element compounds preferably used in the processof the invention as homogeneous catalysts for carrying out the reactionsc) and d) are, e.g., carbonyl complexes, such as

HRh(PPh₃)₃ (CO),

HRuCl(CO)(PPh₃)₃, or

H₂ Ru(CO)₂ (PPh₃)₃, and, very preferably,

RuCl₂ (CO)₂ (PPh₃)₃, as well as organotrioxorhenium compounds of theformula V ##STR9## in which R¹ is a C₁ -C₁₀ alkyl group, anunsubstituted cyclopentadienyl group or a cyclopentadienyl groupsubstituted by 1 to 5 C₁ -C₄ alkyl groups, a C₆ -C₁₀ aryl group or a C₇-C₁₁ aralkyl group. For information on the preparation of theseorganotrioxorhenium compounds reference is made to the processesdescribed in Angew. Chem. 100, 420 (1988), Angew. Chem. 103, 183 (1991)J. Organomet. Chem. 297, C 5(1985), Angew. Chem. 100, 1269 (1 988) andJ. Organomet. Chem. 382, 1 (1990).

Preferred homogeneous catalysts for the execution of the reactions c)and d) in a single process stage are complexes of the transition metalelements mentioned above, particularly those of cobalt, nickel, rhodium,ruthenium, palladium, platinum, and iridium with monodentate orpolydentate, particularly bidentate, phosphine or phosphite ligandsand/or with nitrogenous ligands, in which the (--N═C--C═N--) structureunit is responsible for their property as chelating agent, for example,2,2'-bipyridine or 1,10-phenanthroline, as well as the ligands derivedfrom the said heterocyclic compounds by substitution or anellation.

Suitable ligands are, for example, those suitable for carrying out thepartial reaction a) of the process of the invention and the phosphineligands mentioned in this application in the description of said partialreaction, to which reference is made herewith. Examples of suitable2,2'-bipyridine or 1,10-phenanthroline ligands are those 2,2'-bipyridineor 1,10-phenanthroline ligands mentioned in the description of thepartial reaction a) as being suitable for carrying out said partialreaction a) of the process of the invention as well as their derivativesand structural analogs mentioned loc cit, to which reference is madeherewith.

Suitable phosphite ligands are, e.g., trialkylphosphites,alkyldiarylphosphites, triarylphosphites, alkylbisphosphites,arylbisphosphites, alkylarylbisphosphites. The alkyl group-carryingligands may contain the same or different C₁ -C₁₀, preferably C₁ -C₆,alkyl or cycloalkyl groups. The aryl group-carrying ligands can containthe same or different C₆ -C₁₂ aryl groups, particularly the phenyl ornaphthyl group, or alternatively the diphenyl group. Furthermorephosphite ligands can be used for complexing the transition metals,which carry heterocycloaliphatic groups, such as pyrrolidine,imidazolidine, piperidine, morpholine, oxazolidine, piperazine, ortriazolidine groups or heteroaromatic groups, such as pyrrole,imidazole, oxazole, indole, pyridine, quinoline, pyrimidine, pyrazole,pyrazine, pyridazine, or quinoxazoline groups together with other alkylor aryl groups. The alkyl or aryl groups of the phosphite ligands can beunsubstituted or can carry substituents which are inert under theconditions of the reaction, such as C₁ -C₄ alkoxy, di-(C₁ -C₄alkyl)amino, C₁ -C₆ alkyl, hydroxy, nitro, cyano, or sulfonate groups.The sulfonate-substituted phosphite ligands and their complexes aregenerally water-soluble. Suitable phosphite ligands are, e.g.,trimethylphosphite, triethylphosphite, tripropylphosphite,triisopropylphosphite, tributylphosphite, tricyclopentylphosphite,tricyclohexylphosphite, triphenylphosphite as well as the mono- andbis-phosphite ligands described in EP-A 472,071, EP-A 213,639, EP-A214,622, DE-A 2,733,796, EP-A 2261, EP-A 2821, EP-A 9115, EP-A 155,508,EP-A 353,770, U.S. Pat. No. 4,318,845, U.S. Pat. No. 4,204,997, and U.S.Pat. No. 4,362,830.

When carrying out the reactions c) and d) with catalysts comprisinghomogeneous phosphine or phosphite complexes soluble in the reactionmedium it may be advantageous to add an additional phosphine orphosphite to the reaction mixture, preferably the phosphine or phosphiteserving as ligand in the homogeneous catalyst employed. Such an additioncan cause prolongation of the useful life of the homogeneous catalystand moreover improve the selectivity of the isomerization of the adductII toward the enamine IV and the selectivity in the combinedhydrolysis/hydrogenation of the enamine IV to n-butanol and thus theoverall selectivity of the process. A similar advantageous effect can beinduced by the addition of carbon monoxide to the reaction mixture,particularly when making use of carbonyl group-containing transitionmetal element complexes as homogeneous catalysts.

Although the addition of hydrogen to the reaction mixture is unnecessaryfor the synthesis of the end product n-butyraldehyde, the feed of smallamounts of hydrogen can, optionally together with the addition of smallamounts of carbon monoxide when making use of carbonyl group-containinghomogeneous catalysts, lead to a prolongation of the useful life ofthese homogeneous catalysts. Conveniently, synthesis gas can be used forthis purpose.

To achieve the aforementioned effects, the phosphine or phosphite is ingeneral added in a molar amount with respect to the phosphine orphosphite complex of the transition metal element of from 2 to 100times, preferably from 2 to 20 times and more preferably from 2 to 1 0times. If the transition metal element complex serving as homogeneouscatalyst is produced in situ in the reaction mixture, it is advantageousto use a correspondingly high excess of phosphine or phosphite ligandover the respective transition metal element.

The transition metal catalysts soluble which are homogeneously solublein the reaction medium are generally employed in amounts of, preferably,from 0.0001 to 0.5 mol %, preferably from 0.0002 to 0.2 mol % withrespect to the adduct II fed to the reactor. It will be obvious to theperson skilled in the art that the amount of homogeneous catalyst to beadded is governed in each case by the catalytical activity of thehomogeneous catalyst used. Depending on the nature of the homogeneouscatalyst employed it will thus be advantageous to add a larger orsmaller amount of catalyst to the reaction mixture. Advantageously theoptimum amount is determined in a preliminary test for each homogeneouscatalyst to be used.

The execution of the reactions c) and d) in a single process stage withthe aid of the said homogeneous catalysts can be carried out batchwise,e.g., in stirred vessels, or continuously, e.g., in tubular reactors orloop reactors, at temperatures of in general from 80° C. to 150° C. andunder a pressure of generally from 5 to 100 bar, preferably from 10 to60 bar. The isomerization of the adduct II to the enamine IV and itsconversion to n-butyraldehyde and/or n-butanol in a single process stagecan take place in the presence or absence of added solvents, such asaliphatic or aromatic hydrocarbons, e.g., toluene, benzene, orcyclohexane, alcohols, e.g., butanols, particularly n-butanol, higherfatty alcohols or glycols, ethers, e.g., dibutyl ether, tetrahydrofuran,dioxane or low molecular weight poly(alkylene glycol)s, halogenatedaliphatic or aromatic hydrocarbons, e.g., chloroform, dichloromethane,chlorobenzene, dichlorobenzene, sulfoxides, or sulfones, e.g., dimethylsulfoxide or sulfolane.

If no further solvents are added in the single-stage conversion of theadduct II to the end products n-butyraldehyde and/or n-butanol, thereactants themselves, i.e. the adduct II of the enamine IV and the wateremployed in the invention for the hydrolysis of the enamine IV, and thedesired products of the reaction, cause dissolution of the homogeneouscatalysts employed in accordance with the invention.

For the preparation of the end products n-butyraldehyde and n-butanolwater is added to the reaction mixture in a molar ratio, based on adductII fed to the reactor, generally of from 1:1 to 100:1 and preferablyfrom 2:1 to 20:1 and more preferably from 3:1 to 10:1. When the processis carried out batchwise the water can be placed in the reactor togetherwith the other reactants, the adduct II and the homogeneous catalyst,but it may be advantageous to meter the water to the reactor followingcommencement of the reaction. The decision as to which of these modi ofoperation is to be used will depend on the catalyst used in each caseand the pressure and temperature conditions employed. Advantageously theoptimum mode of operation is determined for each catalyst used in apreliminary test. Similarly, when the process is carried outcontinuously, e.g., in a tubular reactor or a cascade of reactors, thewater can be passed to the reactor together with the other reactants, ormetered to the reactor via a separate inlet only after the reactantshave resided in the reactor for a specific period of time.

If the desired end product is n-butanol, not only is water added to thereaction mixture for the hydrolysis of the enamine IV, but also hydrogenis added in a molar ratio, based on adduct II added to the reactor,generally of from 1:1 to 100:1, preferably from 1:1 to 10:1 and morepreferably from 1:1 to 3:1. This admixture can take place, when using abatch mode of operation, by forcing in the necessary amount of hydrogeninto the reactor or by dispersing the hydrogen in the reaction medium,for example, by means of bubble-cap columns or by means of loop reactorsequipped with nozzles for dispersing the hydrogen. The admixture of thehydrogen can take place when the reactor is charged with the otherreactants, i.e. the adduct II, the water, and the homogeneous catalyst.Alternatively, the hydrogen can be subsequently introduced into thereaction apparatus, advantageously following commencement of thereaction. The decision as to which of these modi will be used in eachinstance, will depend on the catalyst used and the pressure andtemperature conditions used in each case as well as on the design of thereactor. Conveniently, the optimum mode of operation is determined in apreliminary test. Similarly, when the process is carried outcontinuously, e.g., in a tubular reactor, a bubble-cap column reactor ora packed column, the hydrogen can be introduced into the reactortogether with the other reactants or else fed to the reactants in thereactor through a separate inlet after these have been present thereinfor a specific period of time.

If the desired end product is a mixture of n-butanol andn-butyraldehyde, the proportions of these products in the productmixture can be controlled, for example via the feed of hydrogen and/orthe temperature of reaction used. If substoichiometric amounts ofhydrogen are employed, only a portion of the starting material will, ofcourse, be hydrogenated to n-butanol, and by using a lower temperatureof reaction the velocity of the hydrogenation reaction can be sloweddown to such a degree that only a portion of the starting material ishydrogenated to n-butanol.

Execution of the partial reactions c) and d) in at least two processstages using said homogeneous catalysts may be effected batchwise, e.g.in stirred boilers, or continuously, e.g. in stirred boilers or tubularreactors.

The isomerization of the adduct II to the enamine IV in the first stagecan take place in the presence or absence of added solvents, such asaliphatic or aromatic hydrocarbons, e.g., toluene, benzene, orcyclohexane, alcohols, e.g., butanols, particularly n-butanol, higherfatty alcohols or glycols, ethers, e.g., dibutyl ether, tetrahydrofuran,dioxane or low molecular weight poly(alkylene glycol)s, halogenatedaliphatic or aromatic hydrocarbons, e.g., chloroform, dichloromethane,chlorobenzene, dichlorobenzene, sulfoxides, or sulfones, e.g., dimethylsulfoxide or sulfolane.

The isomerization of the adduct II to the enamine IV can be carried outin a phosphine melt instead of in the above conventional solvents. Thismode of operation can be used to advantage when phosphine-containinghomogeneous catalysts are used. The phosphine then acting as solvent cangenerally be chosen arbitrarily, but is it preferred to use the samephosphine for the melt as is employed as ligand in the transition metalelement complex acting as catalyst.

Then, in the second stage, the hydrolysis of the enamine IV tobutyraldehyde or the combined hydrolysis/hydrogenation thereof to formn-butanol can take place using a homogeneous catalyst of the typedescribed above for the single-stage method.

The procedure described for the single-stage process can be employed toobtain n-butyraldehyde and/or n-butanol as desired.

The acids used for the hydrolysis of the enamine IV to butyraldehyde canbe, for example, conventional, non-oxidizing Bronsted acids, such ashydrohalic acids, e.g., hydrochloric acid, sulfuric acid, phosphoricacid, perchloric acid, hydrofluoric acid, tetrafluoroboric acid,methanesulfonic acid, or toluenesulfonic acid, or organic acids such asformic acid, acetic acid, propionic acid, or diacids such as oxalicacid. However solid Bronsted acids, particularly organic or inorganiccation exchangers, or acetic or oxalic acid, are preferably employed.

Since the optimum amount of acid to be used varies greatly from acid toacid, the person skilled in the art will have to determine the necessaryamount in each case in a preliminary test.

By organic cation exchangers we mean pulverulent, gel-like, ormacroporous, polymeric polyelectrolytes, which carry Bronsted acidicfunctional groups, such as sulfonic or phosphonic acid groups orcarboxyl groups, on a polymeric matrix, for example, sulfonatedphenol-formaldehyde resins, sulfonated poly(styrene-co-divinylbenzene)s, sulfonated polystyrene, poly(perfluoroalkylenesulfonicacid)s, or sulfonated coals. In the process of the invention thesecation exchangers can be used in the form of commercial products such asare available under the trade names Amberlite®, Dowex®, Amberlyst®,Lewatit®, Wofatit®, Permutit®, and Nafion®. Advantageously, theexchangers are used in the process of the invention in their protonizedform, the so-called H⁺ form. Suitable organic cation exchangers are, forexample, the commercial products Amberlite® 200, Amberlite® IR 120,Amberlite® IR 132 E, Lewatit® SC 102, Lewatit® SC 104, Lewatit® SC 108,Lewatit® SPC 108, Lewatit® SPC 112, Lewatit® SPC 118 and Amberlyst® 15.

In the process of the invention there may be used, if desired, solidshaving a Bronsted acid effect instead of said organic acidic cationexchangers, examples of such solids being zeolites, e.g. β-zeolites orY-type zeolites in the H⁺ form, bleaching earths such as benonites,montmorillonites, or attapulgites, non-zeolitic molecular sieves on aphosphate basis such as are the subject of U.S. Pat. No. 4,440,871, U.S.Pat. No. 4,310,440, U.S. Pat. No. 4,576,029, U.S. Pat. No. 4,554,143,U.S. Pat. No. 4,500,651, EP-A 158,976, EP-A 158,349, and EP-A 159,624,and also acidic or acid-impregnated metal oxides, the preparation ofwhich is described in U.S. Pat. No. 4,873,017. Preferred Bronsted-acidicinorganic solids are γ-zeolites or Y-type zeolites in their H⁺ form,particularly γ-zeolites in their H⁺ form. γ-Zeolites can be prepared,for example, by the method described in U.S. Pat. No. 4,891,458.

When liquid or dissolved Bronsted acid catalysts are used in thispartial reaction of the process of the invention, particularly aceticacid or oxalic acid, the procedure adopted is generally as follows: theenamine IV is fed, in liquid form, together with water, to a quantity ofthe acid and the products formed are removed from the reaction zone bydistillation or stripping. This can be effected in conventional reactorssuch as bubble-cap columns, loop reactors, and the like. It isadvantageous to introduce the mixture into the acid via, e.g. jetnozzles. The products may also be separated from the solution of theBronsted acid in a phase separator. If desired, a cascade of stirredboilers can be used instead of a bubble-cap column or loop reactor.

If, however, solid Bronsted acids are used in the process of theinvention in the form of said organic or inorganic catalysts,particularly organic ion exchangers, these are preferably placed in afixed bed, through which the liquid reaction mixture flows eitherupwardly or downwardly. The fixed catalyst bed can be installed, forexample, in a tubular reactor or, preferably, in a cascade of reactors.

On completion of the reaction, the reaction product is generallypurified by distillation, whilst the homogeneous catalyst used isrecovered from the bottoms of the distillation to be used again ifdesired, for example, by recycling the catalyst solution to the processstage involving the isomerization of the adduct II to the enamine IV andits hydrolysis and hydrogenation. If recycling of the catalyst isdesired in the process of the invention, a solvent can be added to thereaction mixture, advantageously, this preferably being a solvent whichboils at a higher temperature than the reaction products n-butanol andn-butyraldehyde. If the homogeneous catalyst used is chemically andthermally stable under the conditions of the distillation, the additionof a high-boiling solvent can be dispensed with and the homogeneouscatalyst can be recycled in solid form to the reaction. Whenpurification is effected by distillation, the reaction productn-butyraldehyde and/or n-butanol is also separated from the amine R¹ R²NH I liberated in the previous process stage from the enamine IV byhydrolysis or hydrogenation, which is recycled to the first processstage of the process of the invention involving the chemical addition ofthe amine R¹ R² NH I to 1,3-butadiene. Valuable by-products of theprocess according to the invention can be obtained during purification,by distillation, of the reaction product, these being the octanols, orthe aldehydes corresponding to these alcohols, formed as a result ofpartial dimerization of the butadiene.

In another embodiment of the process of the invention the isomerizationof the adduct II to the enamine IV and its hydrolysis or hydrogenationto n-butyraldehyde and/or n-butanol is carried out in a single processstage using a heterogeneous catalyst, whilst the process can be carriedout either in the liquid phase or in the gaseous phase.

We have found, surprisingly, that the catalysts that can be used bothfor the isomerization of the adduct II to the enamine IV and for thehydrolysis of the enamine IV to n-butyraldehyde or for the combinedhydrolysis/hydrogenation of the enamine IV to n-butanol are commonlyused heterogeneous hydrogation catalysts substantially insoluble in thereaction medium. Of these hydrogenation catalysts those are preferredwhich contain one or more Group Ib, VIb, VIIb, and VIIIb elements,optionally in combination with one or more Group Vb elements,particularly copper, chromium, molybdenum, tungsten, rhenium, ruthenium,cobalt, nickel, rhodium, iridium, palladium, and/or platinum, optionallyin combination with iron.

The more active hydrogenation catalysts such as nickel or the platinummetals can be advantageously doped with main group elements capable ofacting as catalyst poisons, so as to partially poison such catalysts.This makes it possible to achieve a higher degree of selectivity in thecombined hydrolysis/hydrogenation of the enamine IV to n-butanol.Suitable main group elements are, e.g., the chalcogenes, such as sulfur,selenium, and tellurium, as well as the elements phosphorus, arsenic,antimony, bismuth, tin, lead, and thallium.

In the process of the invention use can be made of, e.g., so-calledprecipitation catalysts to act as the heterogeneous catalysts. Suchcatalysts can be prepared by precipitating their catalytically activecomponents in the form of, e.g., difficultly soluble hydroxides, oxidehydrates, basic salts, or carbonates from their salt solutions,particularly from solutions of their nitrates and/or acetates, forexample, by the addition of solutions of alkali metal and/or alkalineearth metal hydroxides and/or carbonates, then drying the precipitatesobtained and converting them, by calcination at generally from 300° to700° C., particularly from 400° to 600° C., to the respective oxides,mixed oxides and/or oxides of mixed-valency, which are reduced, e.g., bytreatment with reducing agents, such as hydrogen or hydrogen-containinggases, at usually from 20° to 700° C., particularly at a temperature offrom 20° to 300° C., to the respective metals and/or oxidic compoundshaving a low degree of oxidation and are thus converted to the actualcatalytically active form. During this process reduction is usuallycarried out until no more water is formed. In the preparation ofprecipitation catalysts containing a support material, the precipitationof the catalytically active components can take place in the presence ofthe respective support material. Alternatively however, thecatalytically active components can be advantageously precipitatedconcurrently with the support material from the respective saltsolutions.

In the process of the invention it is preferred to use hydrogenationcatalysts in which the metals or metal compounds catalyzing thehydrogenation are present as deposits on a support material. Apart fromthe aforementioned precipitation catalysts containing a support materialin addition to the catalytically active components, suitable catalystsfor the process of the invention are generally those supported catalystsin which the catalytically effective components have been applied to asupport material by, say, impregnation.

The manner in which the catalytically active metals are applied to thesupport is not usually important and can comprise a wide variety ofmethods. The catalytically active metals can be applied to these supportmaterials, e.g., by impregnation with solutions or suspensions of thesalts or oxides of relevant elements, drying and then reducing the metalcompounds to the respective metals or compounds of a lower degree ofoxidation by means of a reducing agent, preferably with the aid ofhydrogen, hydrogen-containing gases or hydrazine. Another possibility toeffect application of the catalytically active metals on to thesesupports consists in impregnating the supports with solutions ofthermally readily decomposable salts, e.g., with nitrates or withthermally readily decomposable complex compounds, e.g., carbonyl orhydrido complexes of the catalytically active metals, and heating theimpregnated support to temperatures of from 300° to 600° C. for thepurpose of thermally decomposing the adsorbed metal compounds. Thisthermal decomposition is preferably carried out under a blanket ofprotective gas. Suitable protective gases are, e.g., nitrogen, carbondioxide, hydrogen, or the noble gases. Furthermore the active metals canbe deposited on to the catalyst support by vapor deposition or by flamespraying.

The content of catalytically active metals in these supported catalystsis theoretically irrelevant to the success of the process according tothe invention. It will be apparent to the person skilled in the art thathigher contents of catalytically active metals in these supportedcatalysts lead to higher space-time yields than lower contents.Generally however, supported catalysts are used whose content ofcatalytically active metals is from 0.1 to 80wt % and preferably from0.5 to 30wt %, based on the total catalyst. Since these content datarefer to the total catalyst including support material, and sincedifferent support materials have very different specific weights andspecific surface areas, these statements can be deviated from upwardlyor downwardly without impairing the results of the process of theinvention. Of course, a number of catalytically active metals can beapplied to the respective support material if desired. Furthermore thecatalytically active metals can be applied to the support, for example,by the processes described in DE-A 2,519,817, EP-A 147,219, and EP-A285,420. In the catalysts described in the aforementioned references thecatalytically active metals are present in the form of alloys, which areproduced by thermal treatment and/or reduction of salts or complexes ofthe above metals deposited on a support by, e.g., impregnation.Activation of the precipitation catalysts and of the supported catalystscan also take place in situ in the reaction mixture due to the hydrogenpresent therein, however, these catalysts are preferably activated priorto use in the process of the invention.

Suitable support materials are generally the oxides of aluminum andtitanium, zirconium dioxide, silicon dioxide, kieselguhr, silica gel,argillaceous earths, e.g., montmorillonites, silicates, such asmagnesium or aluminum silicates, zeolites, such as ZSM-5 or ZSM-10zeolite, and activated charcoal. Preferred support materials arealuminum oxides, titanium dioxides, zirconium dioxide, and activatedcharcoal. It is of course possible to use mixtures of different supportmaterials as supports for catalysts to be used in the process of theinvention, if desired.

Examples of suitable heterogeneous catalysts for execution of thereactions c) and

d) in a single process stage are the following catalysts:

platinum dioxide, palladium on aluminum oxide, palladium on silicondioxide, palladium on barium sulfate, rhodium on activated charcoal,rhodium on aluminum oxide, ruthenium on silicon dioxide or activatedcharcoal, nickel on silicon dioxide, cobalt on silicon dioxide, cobalton aluminum oxide, carbonyliron powder, rhenium black, Raney rhenium,rhenium on activated charcoal, rhenium/palladium on activated charcoal,rhenium/platinum on activated charcoal, copper on kieselguhr, copper onsilica gel, copper on titanium dioxide, copper on zirconium dioxide,copper on magnesium silicate, copper on aluminum silicate, copper onmontmorillonite, copper on zeolite, Raney copper, platinum oxide/rhodiumoxide mixtures, platinum/palladium on activated charcoal, copperchromite, barium chromite, nickel/chromium oxide on aluminum oxide,dirhenium heptoxide (Re₂ O₇), cobalt sulfide, nickel sulfide,molybdenum(VI) sulfide, copper/molybdenum(VI) oxide/silicondioxide/aluminum oxide catalysts, palladium on activated charcoalcatalysts partially poisoned with selenium or lead, and the catalystsdescribed in DE-A 3,932,332, U.S. Pat. No. 3,449,445, EP-A 44,444, EP-A147,219, DE-A 3,904,083, DE-A 2,321,101, EP-A 415,202, DE-A 2,366,264,and EP-A 100,406.

It may be advantageous to use, in the process of the invention,hydrogenation catalysts containing Bronsted and/or Lewis acid centers.When using such catalysts the further addition of a Bronsted or Lewisacid to the reaction mixture is generally unnecessary.

The catalytically active metals themselves can act as Bronsted or Lewisacid centers if, for example when effecting activation of the catalystwith hydrogen or hydrogenous gases, reduction to the respective metalsis not carried to completion. This applies, e.g., to rhenium-containingand chromite-containing catalysts, such as supported rhenium catalystsand copper chromite. In the supported rhenium catalysts the rhenium ispresent in the form of a mixture of rhenium metal with rhenium compoundsat higher oxidation stages, where the latter can display effects such asthose shown by Lewis or Bronsted acids. Moreover, such Lewis or Bronstedacid centers can be introduced into the catalyst via the supportmaterial used. As support materials containing Lewis or Bronsted acidcenters there may be mentioned, e.g., titanium dioxides, zirconiumdioxide, silicon dioxide, the silicates, argillaceous earths, zeolites,and activated charcoal.

Thus we particularly prefer to use, in the process of the invention, ashydrogenation catalysts, supported catalysts which contain Group Ib,VIb, VIIb, and/or VIIIb elements, particularly Group Ib, VIIb, and VIIIbelements deposited on a Bronsted or Lewis-acid support material.Particularly advantageous catalysts are, e.g., rhenium on activatedcharcoal, rhenium on zirconium dioxide, rhenium on titanium dioxide,rhenium on silicon dioxide, copper on activated charcoal, copper onsilicon dioxide, copper on kieselguhr, copper on silica gel, copper ontitanium dioxide, copper on zirconium dioxide, copper on magnesiumsilicate, copper on aluminum silicate, copper on bleaching earth, copperon zeolite, ruthenium on activated charcoal, ruthenium on aluminumoxide, ruthenium on silicon dioxide, ruthenium on titanium dioxide, andalso palladium on activated charcoal catalysts partially poisoned withselenium or lead.

Hydrogenation catalysts, which do not themselves have such Bronsted orLewis acid centers, can be admixed with Lewis or Bronsted acidiccomponents, such as zeolites, aluminum or silicon oxides, phosphoricacid or sulfuric acid. The latter are generally added in amounts of from0.01 to 5 wt %, preferably from 0.05 to 0.5 wt % and more preferablyfrom 0.1 to 0.4 wt %, based on the weight of the catalyst.

Other suitable heterogeneous catalysts for the isomerization of theadduct II to the enamine IV and its hydrolysis or hydrogenation ton-butyraldehyde and/or n-butanol in a single process stage are thosewhich contain in heterogenized form the complex compounds of Group VIband VIIIb transition metal elements which can be used for thehomogeneous catalysis of the complex compounds suitable for use in thisprocess stage, for example, those in which the respective transitionmetal element is attached to a polymeric matrix.

Such polymeric matrices can be resins, such as styrene-divinylbenzeneresins (U.S. Pat. No. 3,725,489) or phenol-formaldehyde resins, to whichthe respective ligands serving to chelate the transition metal elementare preferably attached by covalent bonds, which again form complexeswith the respective transition metals and thus quasi immobilize them.Such heterogenized, polymerically linked transition metal elementcomplex catalysts with 2,2'-bipyridine or 1,10-phenanthroline ligands orheterogenized phosphine or phosphite complexes of the catalyticallyactive transition metal elements can be prepared, e.g., by theprepublished processes mentioned above for the preparation of saidcatalysts in connection with the description of partial reaction a).Organotrioxorhenium(VII) catalysts can, e.g., be attached bycoordinate-bond linkage, by the process described in DE-A 3,902,357, tonitrogenous polymers, such as poly(vinyl pyrrolidone),poly(2-vinylpyridine), poly(2-vinylpyridine-co-styrene), poly(acrylicacid amide)s, polyimides, polyamides, and polyurethanes andheterogenized in this way, and then used in the process of the inventionas heterogeneous catalysts.

Using the said heterogeneous catalysts the isomerization of the adductII to the enamine IV and its hydrolysis or hydrogenation ton-butyraldehyde and/or n-butanol can be carried out in a single processstage continuously or batchwise.

If this reaction is carried out in the liquid phase, the heterogeneouscatalyst can be used in the form of suspended solids in the liquidreaction medium or, preferably, in the form of a fixed bed or a numberof fixed beds. When use is made of a heterogeneous catalyst suspended inthe liquid reaction medium the process can be carried out, e.g., instirred vessels or loop reactors. When use is made of a heterogeneouscatalyst in the form of a fixed bed the reaction mixture is in generalpassed through the fixed catalyst bed either upwardly or downwardly.

Both the hydrogenation of the enamine IV and its hydrolysis orhydrogenation can be carried out in adiabatic or isothermal reactors.Generally the space velocity of the liquid reaction mixture relativelyto the catalyst is equivalent to from 0.01 to 10, preferably from 0.05to 3 and more preferably from 0.08 to 1 kg of amine per liter ofcatalyst per hour. When use is made of the heterogeneous catalysts thereaction can take place in the presence or absence of a solvent.Suitable solvents are the same as those which can be used when carryingout the process under homogeneous catalysis conditions.

As described above with reference to carrying out the reactions c) andd) of the process of the invention using homogeneous catalysis, thewater required for the preparation of the end products n-butyraldehydeand/or n-butanol can be fed to the reactor together with the adduct IIand/or added via separate feed lines, divided into one or more partialstreams, and introduced into the catalyst bed at various points. Thesame applies to the feed of water and hydrogen for the preparation ofthe end product n-butanol.

The water required for the preparation of n-butyraldehyde when carryingout the process under heterogeneous catalysis conditions is fed to thereactor at such a rate that the molar ratio of water to the adduct IIadded is generally from 1:1 to 100:1, preferably from 1:1 to 50:1 andmore preferably from 1:1 to 10:1 . The combined isomerization of theadduct II to the enamine IV and its hydrolysis to n-butyraldehyde in asingle process stage over a heterogeneous catalyst in the liquid phaseis generally carried out at a temperature of from 20° to 400° C.,preferably from 30° to 300° C. and more preferably from 80° to 200° C.and under a pressure of, in general, from 1 to 300 bar, preferably from2 to 1 50 bar, and more preferably from 5 to 100 bar.

The hydrogen required, in addition to water, for the preparation ofn-butanol when carrying out the process under heterogeneous catalysisconditions is fed to the reactor at such a rate that the molar ratio ofhydrogen added to adduct II added is generally from 1:1 to 100:1,preferably from 1.5:1 to 80:1, and more preferably from 2:1 to 40:1. Thecombined isomerization of the adduct II to the enamine IV and itshydrolysis/hydrogenation to n-butanol in a single process stage in aheterogeneous catalyst system in the liquid phase is generally carriedout at a temperature of from 20° to 400° C., preferably from 30° to 300°C. and more preferably from 80° to 200° C. and under a pressure ofgenerally from 1 to 300 bar, preferably from 5 to 250 bar, and morepreferably from 20 to 200 bar. Of course, the quantity of water requiredfor the preparation of n-butanol from the adduct II is the same as thatrequired for the preparation of n-butyraldehyde from the adduct II.

If the desired end product is a mixture of n-butyraldehyde andn-butanol, water and hydrogen are introduced at rates similar to thosementioned above and relate to the rate of feed of the adduct II suchthat the isolation of the two end products in the desired ratio of theproducts is possible. Moreover the ratio of these two end products inthe effluent can also be controlled by using different heterogeneouscatalysts, for example, by using heterogeneous catalysts which possesshigh hydrolysis activity and, in comparison, relatively lowhydrogenation activity. This purpose can be advantageously realized, forexample, by using catalysts that have been inactivated or partiallypoisoned with regard to their hydrogenating properties, e.g., palladiumon activated charcoal catalysts partially poisoned with selenium orlead.

The liquid effluent from this process stage is generally worked up bydistillation, in a manner similar to that described above with referenceto the execution of this process stage using homogeneous catalysts. Ofcourse recycling of the catalyst, which may possibly be convenient andadvantageous when using homogeneous catalysts, is omitted when usingheterogeneous catalysts. Recycling of the amine R¹ R² NH I liberated inthis process stage back to the process stage involving the addition ofthe amine R¹ R² NH I to 1,3-butadiene can be advantageously carried outin a manner similar to that already described with reference to thereaction occurring in this process stage using homogeneous catalysts.

As already mentioned, the isomerization of the adduct II to the enamineIV and its hydrolysis or hydrogenation to n-butyraldehyde and/orn-butanol in a single process stage can be advantageously carried out inthe gaseous phase. To this end conventional reactors for gas phasereactions are used, for example, those in which the catalyst is in theform of a fixed bed or fluidized bed. The reactors can be operatedadiabatically or isothermally. When use is made of a fixed bed catalystsystem, the catalyst can be disposed in a single fixed bed or,advantageously for the purpose of improving the dissipation of the heatof reaction, in a number of fixed beds, for example, in from 2 to 10 andpreferably from 2 to 5 fixed beds. When making use of a number of fixedcatalyst beds or when employing an adiabatic mode of operation of thereactor it may be advantageous to use intra-bed cooling of the reactiongas and/or to effect a temperature decrease of the reaction gas as itleaves one bed but before it reaches the next bed by injectingadditional amounts of cool reactants such as hydrogen, water, adduct II,or enamine IV between the individual fixed beds, in order to increasethe selectivity of the reaction. Heat dissipation may also be effectedby circulating the gas. Advantageously, when use is made of a number offixed beds, the reaction in the individual fixed beds except for thelast fixed bed is only allowed to reach partial conversion, for example,a conversion of from 50 to 98%. The reaction gases can be diluted ifdesired with a gas inert under the reaction conditions, such asnitrogen, saturated hydrocarbons, or argon.

The water required for the preparation of the end productn-butyraldehyde when carrying out the process in the gaseous phase ismetered into the reactor at a rate in relation to the rate of input ofthe adduct II such that the molar ratio of water added to adduct IIadded is generally from 1:1 to 100:1, preferably from 1:1 to 50:1 andmore preferably from 1:1 to 10:1. The water can be fed to the reactortogether with the adduct II and/or, as described above, divided into anumber of partial streams and introduced at different points of thereactor. Generally the space velocity of the reaction gas, essentiallycontaining the adduct II, water, and if desired an inert gas, is from0.01 to 10, preferably from 0.05 to 3 and more preferably from 0.07 to 1kg of reaction gas per liter of catalyst per hour. The reaction,encompassing the isomerization of the adduct II to the enamine IV andits hydrolysis, is generally carried out at a temperature of from 70° to400° C., preferably from 90° to 350° C. and more preferably from 110° to230° C. and under a pressure of in general from 0.5 to 100 bar,preferably from 0.8 to 20 bar and more preferably from 1 to 10 bar.

The hydrogen required for the preparation of the end product n-butanolin addition to water, when carrying out the process in the gaseousphase, is fed to the reactor at a rate relative to the rate of feed ofthe adduct II such that the molar ratio of hydrogen added to adduct IIadded is in general from 1:1 to 200:1, preferably from 1.5:1 to 80:1 andmore preferably from 2:1 to 30:1. Hydrogen can be fed to the reactortogether with the adduct II and/or, as described above, divided into anumber of partial streams and fed in at various points of the reactor.Generally the space velocity of the reaction gas, essentially containingthe adduct II, water, hydrogen, and if desired an inert gas, is from0.01 to 10, preferably from 0.05 to 3, more preferably from 0.07 to 1 kgof reaction gas per liter of catalyst per hour. The reaction,encompassing the isomerization of the adduct II to the enamine IV andits combined hydrolysis/hydrogenation, is generally carried out attemperatures of from 20° to 400° C., preferably from 100° to 350° C. andmore preferably from 150° to 250° C. and under a pressure generally offrom 0.5 to 100 bar, preferably from 0.9 to 30 bar, and more preferablyfrom 1 to 10 bar.

In a manner similar to that described above with reference to theisomerization of the adduct II to the enamine IV and its hydrolysis orhydrogenation to n-butyraldehyde and/or n-butanol in the liquid phaseusing heterogeneous catalysts, the reaction in the gaseous phase can becontrolled by the feed of a mixture containing specific amounts of waterand hydrogen, and by selecting the catalyst to be used such that theeffluent from this process stage contains n-butyraldehyde and n-butanolin the desired proportions.

In order to work up the gaseous effluent it is advantageous to passthis, optionally after depressurization to atmospheric pressure,directly to a distillation apparatus where it is separated bydistillation into its constituent parts.

The catalysts that can be used for the isomerization of the adduct II tothe enamine IV and its hydrolysis or hydrogenation to n-butyraldehydeand/or n-butanol in the gaseous phase in a single process stage arebasically the same heterogeneous catalysts as those employed in the samereaction in the liquid phase. Preferably purely inorganic, mineralcatalysts are used in the gas phase process. Preferred catalysts are,for example, supported catalysts containing Group Ib, VIb, VIIb, and/orVIIIb elements, optionally in combination with one or more Group Vbelements, particularly Group Ib, VIIb, and VIIIb elements present asdeposits on a Bronsted or Lewis acid support material. Particularlyadvantage ous catalysts are, e.g., rhenium on titanium dioxide, rheniumon silicon dioxide, copper on activated charcoal, copper on silicondioxide, copper on kieselguhr, copper on silica gel, copper on titaniumdioxide, copper on zirconium dioxide, copper on magnesium silicate,copper on aluminum silicate, copper on bleaching earth, copper onzeolite, ruthenium on activated charcoal, ruthenium on silicon dioxide,ruthenium on aluminum oxide, ruthenium on zirconium dioxide, rutheniumon magnesium oxide, and ruthenium on titanium dioxide, and alsopalladium on activated charcoal catalysts partially poisoned withselenium or lead.

A further advantageous embodiment of the isomerization of the adduct IIto the enamine IV and its hydrolysis or hydrogenation to n-butyraldehydeand/or n-butanol in a single process stage using heterogeneous catalystscan be achieved both when use is made of the liquid phase process andwhen use is made of the gas phase process and when making use of asingle fixed bed for carrying out these reactions, by employing acombined catalyst bed, consisting of at least 2 layers of differentheterogeneous catalysts which differ in activity and possiblyselectivity for the two reactions c) and d), such that, e.g., in thefirst layer, i.e. that nearest the reactor inlet, the adduct II isinitially isomerized with high activity and selectivity to the enamineIV, which then on passing through the next layer or layers, i.e. that orthose nearest the outlet of the reactor and containing catalysts havinglower isomerization activity but higher hydrolysis activity and/orhigher hydrogenation activity is converted to n-butyraldehyde and/orn-butanol at a high degree of activity and selectivity.

By using a number of contiguous layers of variously active and/orselective catalysts it is possible to achieve accurate control of theheat generated during hydrolysis or the combinedhydrolysis/hydrogenation of the enamine IV, by which means the overallselectivity of the reaction can be increased. This effect can beintensified by e.g., introducing the reactants water and/or hydrogeninto the reactor separately from the adduct II at that zone of thecatalyst bed where the hydrolysis or the combinedhydrolysis/hydrogenation takes place. The water and the hydrogen can bepassed together to the respective zones of the catalyst bed oralternatively individually to different zones of the catalyst bed.Instead of using a combined bed containing all of the differentcatalysts required for catalyzing the individual reactions, it ispossible, in this embodiment, to have the catalysts present in a numberof fixed beds, each containing a different catalyst.

Although the execution of the reactions c) and d) of the processaccording to the invention in a single process stage, e.g., by themethods described above is a preferred embodiment of the process of theinvention, it may be advantageous under certain circumstances to carryout the individual reactions, i.e. the isomerization of the adduct II tothe enamine IV, the hydrolysis of the enamine IV to n-butyraldehyde orthe hydrogenation of the butyraldehyde to n-butanol, in a number ofprocess stages. For example, it is possible to carry out each one ofthese reactions in an individual process stage by first isomerizing theadduct II to the enamine IV in one process stage, then hydrolyzing theenamine IV to n-butyraldehyde and then hydrogenating the n-butyraldehydeto n-butanol, or separating the resulting butyraldehyde or a portion ofsaid butyraldehyde and aldolizing the same in a further stage followedby hydrogenation to 2-ethylhexanol. Such process steps are well known tothe person skilled in the art. Likewise the isomerization of the adductII to the enamine IV can take place in a separate process stage and theenamine IV can then be hydrolyzed to n-butyraldehyde or be furtherprocessed in a hydrolysis/hydrogenation reaction to n-butanol or amixture of n-butanol and n-butyraldehyde. A further variant of theprocess according to the invention comprises carrying out theisomerization of the adduct II to the enamine IV and its hydrolysis ton-butyraldehyde in a single process stage and then hydrogenating then-butyraldehyde thus obtained to n-butanol in a further process stage.

When the partial reactions c) and d) are distributed over a number ofprocess stages a wide variety of operational modi can be used in theindividual process stages. For example, the isomerization of the adductII to the enamine IV can be carried out as desired under homogeneouscatalysis conditions or over heterogeneous catalysts. Also thehydrolysis or the combined hydrolysis/hydrogenation of the enamine IV ton-butyraldehyde and n-butanol can be carried out either: in the liquidphase using homogeneous catalysts or heterogeneous catalysts or: in thegaseous phase.

When the individual partial reactions c) and d) are distributed over anumber of process stages it is also possible to use, in the individualprocess stages, instead of the catalysts described above, which catalyzeboth the isomerization of the adduct II to the enamine IV and itshydrolysis and hydrogenation, catalysts which can catalyze only therespective partial reaction. Thus the enamine IV can be hydrolyzed, forexample, by means of Bronsted acid catalysts, such as mineral acids,e.g., hydrohalic acids, sulfuric acid, dilute nitric acid, phosphoricacid, or heterogeneous Bronsted acids, such as ion exchangers, zeolites,bleaching earths, or acid phosphates, for example, aluminum phosphates,to n-butyraldehyde. In this case the amine is liberated from its acidsalt by the additon of a base.

The amine R¹ R² NH I liberated during hydrolysis or combinedhydrolysis/hydrogenation of the enamine IV is preferably recycled backto the reaction defined as partial reaction a). On account of thepossibility of splitting up the partial reactions of the isomerizationof the adduct II to the enamine IV and its hydrolysis or its combinedhydrolysis/hydrogenation into a number of process steps, a higher degreeof flexibility is obtained when designing a plant for carrying out theprocess of the invention, by which means considerable savings can beeffected.

The n-butyraldehyde produced in the process of the invention can, afterit has been isolated by, say, distillation, be converted to2-ethylhexanol in known manner. Thus n-butyraldehyde may be converted tothe aldol product 2-ethylhex-2-enal at 80° to 130° C. and 3-10bar in thepresence of sodium or potassium hydroxide. This aldol product can thenbe catalytically reduced to 2-ethylhexanol at approximately 200° to 250°C. and 50-200 bar of hydrogen.

Alternatively, a reaction mixture produced by the process of theinvention and containing n-butyraldehyde can be subjected toaldolization and hydrogenation in the manner described above and theproduct can be distilled to isolate it from the impurities present inthe original reaction mixture.

The embodiment is preferred in which the butyraldehyde is prepared byacid hydrolysis of the enamine IV, as described in detail above. In thepresence of the acid present in the reaction mixture, then-butyraldehyde can react to form the aldol product 2-ethylhex-2-enal.While it is desirable to suppress this reaction when n-butyraldehyde isthe desired product, the reaction can be manipulated to ensure that thealdol reaction preferentially occurs. This usually necessitates longerreaction times under otherwise identical reaction conditions.Alternatively, the reaction producing the aldol product can beaccelerated by increasing the temperature or the concentration of acidover that required when the process is operated to give a high yield ofn-butyraldehyde. Due to the wide range of possibilities available in thepreparation of n-butyraldehyde the person skilled in the art will haveto carry out preliminary tests to determine the best reaction conditionsfor attaining high yields of aldol product. The resulting aldol productcan be hydrogenated to 2-ethylhexanol by conventional methods. Theoverall reaction yielding 2-ethylhexanol is effected in a particularlyadvantageous manner when the catalyst used in process stage c) of theprocess of the invention for the preparation of n-butyraldehyde and/orn-butanol is a homogeneous catalyst, e.g., a ruthenium catalyst, whichis also capable of catalyzing the hydrogenation to take place in processstage d), provided that the hydrolysis of the enamine IV is carried outin the presence of an acid and process stage d) is carried out in thepresence of hydrogen as described above for the preparation ofn-butanol. In such a case the conversion of the anamine IV to2-ethylhexanol can be effected in a single stage. Purification andrecycling of the amine I can be carried out in a manner similar to thatdescribed above for the preparation of n-butanol.

Process stage a)

EXAMPLES 1 TO 7 Example 1 Partial Reaction a)

A steel autoclave having a capacity of 0.3 L was filled with 0.50 mol ofthe appropriate amine, 1.25 mol of palladium acetylacetonate, and 2.5mmol of phosphine ligand, and the respective amount of butadiene wasthen forced into the recator. The reaction mixture was stirred at 145°C. under the autogenous pressure of the system. On completion of thereaction, the liquid effluent was analyzed by gas chromatography(Carbowax 20 M, 2 m (percentages by area based on amine)).

                                      TABLE    __________________________________________________________________________                             Selectivity  %!*                             3,N-But-1-                                   1,N-But-2-                Butadiene                     Reaction                          Yield                             enylamine                                   enylamine                                         3,N-Octa-                                               1,N-Octa-                                                     By-pro    Ex.      Amine Ligand                 mmol!                     time h!                           %!                             III   II    dienylamine                                               dienylamine                                                     ducts    __________________________________________________________________________    1 Morpholine            DPPB                706  20   97 3     64    1     21    11    2 Morpholine            DPPP                740  20   82 4     72    1     20    3    3 Morpholine            DPPE                747  20   94 3     64    1     21    11    4 Piperidine            DPPE                736  20   90 3     80    0     12    5    5 Piperidine            DPPE                510  20   79 4     79    0     14    3    6 Piperidine            DPPE                488  10   76 4     80    0     13    3    7 Dipropyl-            DPPE                769  20   67 3     64    0     25    8      amine    __________________________________________________________________________     DPPE = bis(diphenylphosphino)ethane     DPPP = bis(diphenylphosphino)propane     DPPB = bis(diphenylphosphino)butane     *based on amine, percentage by area

Example 8

To a solution of 0.12 g (0.25 mmol) ofbis(di-tert-butylphosphino)methane!palladium dichloride in 4.36 g (50mmol) of morpholine there were added successively 0.107 g (0.55 mmol) ofAgBF₄ und 0.076 g (0.25 mmol) of bis(di-tert-butylphosphino)methane andthen 2.70 g (50 mmol) of butadiene were forced in. Following a reactiontime of 5 h at 80° C. and autogenous pressure there was obtained a yieldof 75% at a selectivity of 1 percent by area of octatriene, 6 percent byarea of (3,N)-(but-1-enyl)-morpholine, 76 percent by area of(1,N)-(but-2-enyl)morpholine, 10 percent by area of octadienylmorpholineand 1 percent by area of by-products, as determined by gaschromatographic analysis.

Example 9

A solution of 8.70 g (100 mmol) of morpholine, 0.076 (0.25 mmol) ofPd(acac)₂ (acac=acetylacetonate), and 0.35 g (0.875 mmol) of DPPE wasadmixed with 0.141 g of p-toluenesulfonic acid and 2.4 g of methanol.After forcing in 5.4 g (100 mmol) of butadiene, the mixture was stirredfor 17 h at 100° C. under autogenous pressure. There is obtained a yieldof 96% at a selectivity of 1 percent by area of octatriene, 3 percent byarea of (3,N)-(but-1-enyl)morpholine, 94 percent by area of(1,N)-(but-2-enyl)-morpholine, 1 percent by area of octadienylamine and1 percent by area of by-products.

Process stage c)

Example 10

A solution of 3.06 g (21.7 mmol) of (1,N)-(but-2-enyl)-morpholine, 0.023g (0.024 mmol) of HRuCl(CO)(PPh₃)₃ and 0.034 g (0.125 mmol) oftriphenylphosphine was admixed with 20 g of water and the mixture wasstirred at 12 bar of hydrogen and 150° C. Following a reaction period of20 h there was obtained a yield of 90% at a selectivity of 64 percent byarea of 1-butanol, 4 percent by area of (1,N)-(but-1-enyl)morpholine and32 percent of N-butylmorpholine, as determined by gaschromatographicanaylsis. The morpholine was recovered.

Example 11

Under a blanket of argon, 19 g (122 mmol) of(1,N)-(but-2-enyl)-morpholine were caused to react in a melt of 30 g(114 mmol) of triphenylphosphine and 1.5 g (1.63 mmol) of HRh(PPh₃)₃ COover a period of 245 min at 120° C. with stirring. The products werethen removed by distillation under reduced pressure (15 mbar) and atemperature of up to 120° C. and analyzed by gas chromatography. Thefollowing results were achieved: the yield of(1,N)-(but-2-enyl)-morpholine was 98.1%, apart from(1,N)-(but-1-enyl)morpholine no other product was found (selectivity100%).

Process stage d)

Example 12

2 g (15.9 mmol) of (1,N)-(but-1-enyl)-morpholine were heated with 5 g(278-mmol) of water in the presence of 14 g of 1.4-dioxane and 0.5 g ofBayer Catalyst No. 2611 (acid ion exchanger) for 4 h to a temperature of120° C. The two liquid phases of the original mixture become a singlephase. GC analysis showed a yield of 75% at a selectivity of 31 percentby area of n-butyraldehyde and 69 percent by area of 2-ethylhex-2-enal.morpholine was recovered.

Process stages c) and d)

Example 13

30 g (50 mL) of a copper-on-silica-gel catalyst having a copper content(calculated as CuO) of 26 wt %, were placed in a reactor, and thecatalyst was activated over a period of 18 h with forming gas (5%hydrogen, 95% nitrogen) at atmospheric pressure and a temperaturestarting from 30° C. and reaching a final value of 190° C. Followingactivation the gas flow was switched to pure hydrogen.

1.5 g/h of water and 2.75 g/h of (1,N)-(but-2-enyl)-morpholine were thenfed, at atmospheric pressure, to the reactor held at 190° C. via apreheater held at 150° C. At the same time a hydrogen stream of 8 L/hwas passed into the reactor. Following cooling, the single-phase liquideffluent was analyzed by gas chromatography. At a yield of 60% there wasachieved a selectivity of 54 percent by area of 1-butanol, 4 percent byarea of (1,N)-(but-1-enyl)-morpholine and 42 percent by area ofN-butylmorpholine.

We claim:
 1. A process for the preparation of n-butyraldehyde and/orn-butanol, whereina) 1,3-butadiene is caused to react with an amine ofthe formula I

    R.sup.1 R.sup.2 NH,                                        I

in which R¹ and R² independently denote hydrogen, optionally substitutedaliphatic or cycloaliphatic radicals, or aryl or aralkyl radicals or arelinked to form a nitrogen-containing bridging member, which bridgingmember can contain an additional nitrogen atom and/or oxygen atom, thenumber of bridging atoms being from 3 to 6 at elevated temperature andunder superatmospheric pressure in the presence of a compound of a GroupVIIIb element to form a mixture of the adducts of the formulas II##STR10## and III ##STR11## b) the adduct III is isomerized to theadduct II c) the adduct II is isomerized in the presence of ahomogeneous or heterogeneous transition metal element catalyst in theliquid phase or in the presence of a heterogeneous catalyst containing atransition metal element in the gaseous phase to form the enamine of theformula IV ##STR12## and d) n-butyraldehyde and/or n-butanol is/areproduced from this enamine IV by the reaction thereof with hydrogen andwater or water only in the presence of a homogeneous or heterogeneoustransition metal element catalyst in the liquid phase or in the presenceof a heterogeneous transition metal element catalyst in the gaseousphase, in the presence of an acid or in the presence of one of saidcatalysts and an acid, and the amine I is liberated, and the liberatedamine I is recycled to the stage defined above as reaction a).
 2. Aprocess as defined in claim 1, wherein the reaction of 1,3-butadienewith an amine R¹ R² NH I is carried out in the presence of a catalystcomprising an alkyl, aryl, or arylalkyl phosphine complex of rhodium,ruthenium, nickel, palladium, iridium, or platinum.
 3. A process asdefined in claim 1, wherein the adduct III is separated from the adductII and the adduct III is then recycled to the reaction a) and isisomerized therein to the adduct II.
 4. A process as defined in claim 1,wherein the reactions c)--isomerization of the adduct II to the enamineIV--and d)--hydrolysis or combined hydrolysis/hydrogenation of theenamine IV to n-butyraldehyde and n-butanol--are carried out in a singleprocess stage.
 5. A process as defined in claim 1, wherein the reactionsc) and d) are carried out in the presence of a heterogeneous catalystcontaining copper.
 6. A process as defined in claim 1, wherein thereaction c) and d) are carried out in the liquid phase in the presenceof a homogeneous catalyst soluble in the reaction medium, which catalystis a mono- or polydentate phosphine or phosphite complex of a Group Ib,VIb, VIIb, and VIIIb element.
 7. A process as defined in claim 1,wherein the partial reactions d) is carried out in the presence of anacid ion exchanger.
 8. A process for the preparation of 2-ethylhexanol,wherein 1,3-butadiene is caused to react with an amine of the formula I

    R.sup.1 R.sup.2 NH,                                        I

in which R¹ and R² independently denote hydrogen, optionally substitutedaliphatic or cycloaliphatic radicals, or aryl or aralkyl radicals or arelinked to form a nitrogen-containing bridging member, which bridgingmember can contain an additional nitrogen atom and/or oxygen atom, thenumber of bridging atoms being from 3 to 6 at elevated temperature andunder superatmospheric pressure in the presence of a compound of a GroupVIIIb element to form a mixture of the adducts of the formulas II##STR13## and III ##STR14## b) the adduct III is optionally isomerizedto the adduct II c) the adduct II is isomerized in the presence of ahomogeneous or heterogeneous transition metal element catalyst in theliquid phase to form the enamine of the formula IV ##STR15## e)n-butyraldehyde is produced from this enamine IV by the reaction thereofwith water in the presence of the catalyst used in partial reaction c)and in the presence of an acid, f) the n-butyraldehyde is converted tothe aldol product 2-ethylhex-2-enal, g) the said aldol product ishydrogenated to 2-ethylhexanol, amine Ibeing liberated, which amine I isrecycled to the stage defined above as reaction a).